Finds the top X unanswered tags ("top" by number of questions), and then counts the number of answers given by each tag respondent.
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DECLARE @minQuestionCount int = 500 DECLARE @topN int = 50 -- For top n most populous tags SELECT uqt.TagName, ust.UserId, ust.AnswersCount FROM ( -- All unanswered questions grouped by tag SELECT TOP (@topN) t.TagName AS TagName, COUNT(1) AS UnansweredCount, t.Count AS QuestionCount FROM Posts q INNER JOIN PostTags pt ON q.Id = pt.PostId INNER JOIN Tags t ON pt.TagId = t.Id WHERE (q.PostTypeId = 1) AND (q.ClosedDate IS NULL) AND NOT EXISTS ( SELECT * FROM Posts a WHERE (a.ParentId = q.Id) AND ((a.Score > 0) OR (a.Id = q.AcceptedAnswerId)) ) GROUP BY TagName, t.Count ORDER BY QuestionCount DESC ) uqt, ( -- All users grouped by tag SELECT t.TagName AS TagName, u.Id AS UserId, COUNT(u.Id) AS AnswersCount FROM Tags t JOIN PostTags pt ON pt.TagId = t.Id JOIN Posts p ON p.Id = pt.PostId JOIN Posts as Answers ON Answers.ParentId = p.Id JOIN Users u ON u.Id = Answers.OwnerUserId GROUP BY t.TagName, u.Id ) ust WHERE uqt.QuestionCount > @minQuestionCount AND ust.TagName = uqt.TagName ORDER BY uqt.QuestionCount DESC, ust.AnswersCount DESC